This invention relates to a method for casting and rolling a compound metal bar and rod which comprises a core and a sheath which completely encases the core. The invention more particularly is a method for casting and rolling a compound metal bar which comprises a core and a sheath which completely encases the core and which together form a unitary metal matrix.
Various methods have been used in the past to produce bar having a compound structure but such methods have typically produced a product in which there was a mechanical joining of the core and sheath. Such products have generally been produced by either plating or dipping processes but on occasion these products have been produced by casting continuous lengths of bar using the method disclosed in U.S. Pat. No. 3,421,571 and the apparatus disclosed in U.S. Pat. No. 3,421,571 and the apparatus disclosed in U.S. Pat. Nos. 3,295,173 and 3,295,174. Additionally, apparatus related to pouring molten metal into a casting machine is disclosed in U.S. Pat. Nos. 3,428,111, 3,431,971 and 3,548,919. Related apparatus is also discussed in U.S. Pat. Nos. 105,112, 112,054, 1,507,456, 1,702,528 and 2,348,178; British Pat. No. 948,116 and Italian Pat. No. 566,874.
The method disclosed in U.S. Pat. No. 3,421,571 involves continuously forming a partially stabilized tube-like sheath of cladding metal and filling it with a core metal and cooling both into a bar. Critical to this method is the partial oxidation of the interior surface of the cladding metal so that mixing of the cladding and core metals is physically prevented by an oxide layer located between the two. Such procedures have resulted in a usable, but metallurgically unstable and tenuous union between the cladding metal and the core metal. Additionally, difficulties have been encountered with the prior art bar which relate to the drawing of the bar into smaller diameter wire of various sizes, particularly when it is desired to have the wire product clad with a metal composition different from the composition of the core metal.